Gem cutters  dop



March 24, 1964 H. A. IPRINTZ GEM CUTTERS no? Filed 001;. 13. 1961 INVENTOR. HILLARD A. PRINTZ ATTORNEY United States Patent 3,125,836 GEM CUTTERS D01 Hillard A. Printz, 201 E. Park Ave, New Castle, Pa. Filed Oct. 13, 1961, Set. No. 144,965 9 Claims. (Cl. 51-229) This invention pertains to gem cutting and more particularly to a novel and improved dop for cutting gems.

In the gem cutting art a flat, rotatable disc known as a lap is employed. In diamond cutting the lap is usually referred to as a skaif or a wheel. For gem cutting an abrasive is placed on the upper face of the lap. A rough gem to be cut is held against the face of the lap as the lap is rotated and the abrasive carried on the lap cuts away portions of the uncut gem. With sapphires and softer gems, softer abrasives are subsequently used for a polishing operation.

A device known as a dop or dop assembly is used to position the uncut gem against the rotating lap. The dop assembly includes a removable dop stick. The standard dop stick is a short quarter inch shaft having a circular pad perpendicularly secured on one end. The gem to be out is secured to the pad by means of an adhesive. The adhesive is often a dopping wax. Thus, the dop stick comprises a handle by means of which a gem is held for cutting, sanding and polishing.

Prior to the actual cutting of the gem, the general shape of the gem may be roughed out on a silicone carbide wheel. For preforming, as the roughing-out process is called, the gem is held against the periphery of the wheel by hand holding the dop stick to which it is secured. Water may be fed to the wheel to keep the gem from heating and loosening the dopzping wax.

The gem is now ready for the facet cut-ting operation. In the usual faceting operation the dop stick with the gem secured to it is inserted in the dop assembly. The dop assembly is rigidly attached in the chuck of a faceting mechanism. The faceting mechanism rigidly positions the gem against the moving lap for accurately cutting the desired facets. After preforming and faceting, or other cutting, the gem is sanded and polished.

A new and improved dop assembly which may be used with a faceting head is the subject of my co-pending application No. 74,138, filed December 6, 1960.

With the prior art devices hand holding the tiny dop stick during preforming enables the gem cutter to only slightly preform the rough, uncut gem. Most of the actual shaping of the gem must be done only by the very skilled and/or by the faceting mechanism. Further, where a general-1y round finished gem is desired the dop assembly must be hand held during the cutting, sanding and polishing operations. With prior known devices only the highly skilled gem cutter has been able to cut a perfectly round gem.

The do-p assembly of this invention enables a relatively unskilled gem cutter to not only accurately preform an uncut gem but also to sand and polish a round gem.

The outer housing of the dop assembly is of a size and shape which enables it to be comfortably held by one of the gem cutters hands. The shaft of the dop stick is inserted in the dop assembly housing and it operatively secured to a control knob. Turning the control knob rotates the dop stick so as to control the manner in which the uncut gem is held against the particular cutting wheel being used.

A special frictionless mounting of the dop stick in the housing of the dop assembly permits the dop stick to rotate freely. When a gem, as secured to the hand dop assembly of the invention, is held against a moving abrasive surface, the motion of the surface causes the gem to spin.

Because a spin is imparted to the gem cutting, sanding "Ice and polishing operations are quickly, easily and accurately performed. By coordinating the movement of the hand with the spin of the gem new and unusual gem shapes may be obtained. Also, many of the standard shapes are obtained more quickly and accurately. For example, by placing the hand holding the dop assembly on a rest and rolling the dop body slightly in toward the center of the cutting wheel a perfectly round surface can be ground on the gem. With a little practice even an amateur can grind a perfectly round gem.

Accordingly, it is an object of this invention to provide a hand-held dop assembly which may be used to preform, sand and polish uncut gems.

It is another object of this invention to provide a handheld dop assembly wherein the gem will spin freely when placed against a moving abrasive surface.

It is still a further object of the invention to provide a hand-held dop assembly which enables the unskilled gem cutter to cut perfectly rounded gems.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view showing the dop assembly of this invention in use; and,

FIGURE 2 is an elevational view in section showing the dop assembly of this invention.

Referring now to the drawing and particularly to FIG- URE 2, an outer cylindrical housing is shown at 10. Outer housing It} will be of a size which may be conveniently held in the hand as shown in FIG. 1. Two ball bearing assemblies 11 and 22 are provided and are pressed one into each end of the outer housing 10. One bearing assembly it is flush with the end of housing 10. The other bearing assembly 22 is pressed further into the interior of the outer housing.

A spindle 12 is journaled in the ball bearing assemblies 1-1 and 22 and extends beyond outer housing ll) at both ends. A spring clip 14- is removably secured around spindle 12. adjacent ball bearing assembly 22. which is further to the interior of the outer housing 10. The spring clip '14 provides a seat for bearing assembly 22. A water seal 15 is also pressed into the outer housing 10 and is positioned adjacent the ball bearing assembly 22 and flush with the end of outer housing ill. The water seal 15 includes a sleeve which may be made of synthetic plastic, rubber or other suitable material and which surrounds the spindle 12 to prevent water from entering the outer housing 10 and damaging the ball bearing assembly 11. The spindle 12 is provided with a center bore 13.

A dop stick 16 is provided and is removably secured in the center bore 13 of the spindle 12 by means of a setscrew 17. The dop stick 16 comprises a shaft 18 and a circular pad 19 upon which the gem to be ground is adhesively secured as by wax.

Having the dop stick l6 removable permits it to be handheld for the very rough preforming of the uncut gem. After rough preforming the dop stick 16 is placed in the hand dop assembly of the invention to finish preforming the uncut gem. The dop stick is also placed in the hand dop assembly to sand and polish the gem.

When [final preforming is completed the gem as secured to the same doprstick 16 may be transferred to a dop assembly of the type described in the referenced copending patent application. When so transferred, the dop is attached to a facet cutting mechanism for the final cutting of the gem. Thus, the removable dop stick 16 permits the gem to be transferred from one operation to another without having to break the adhesive bond.

The preformed gem is not usually polished before faceting. However, if the preformed gem is sanded and polished the facet cutting operation is made much easier.

This is because there is good contrast between the facets as they are being cut and the remaining polished surface. Therefore, as the polished surface is ground away during faceting, the size and. shape of the facets are easily noticeable by eye. Such a contrast does not exist when the uncut gem has only been preformed, or even sanded, before faceting. With the hand dop assembly of the invention little time and effort is required for sanding and polishing and the preformed gem may always be polished before faceting.

A rotating knob 20 is removably secured to the other end of spindle 12. The knob 24B is used to preform the gem secured to the pad 19 on the dop stick 16. The gem cutter will grasp the dop assembly in one hand and place the gem against the rotating wheel. He then uses his other hand to turn knob 2%} to obtain a particular shape or form of the gem. Once the gem is nearly the shape desired it is permitted to spin against the wheel until the curvature of the gem surface is uniform. Finally, the gem is allowed to spin against a sander and then a polishing lap.

When a perfectly round gem is desired, the dop assembly will be held as in FIGURE 1 with the hand against a rest. The body of the hand dop assembly is rolled slightly in toward the center of the rotating wheel until the desired rounded eifect is obtained.

An end cap 21 is removably secured around the rotating knob end of the outer housing 10. The function of the end cap is to shield the rotating knob from the hand when the hand dop assembly is held in the position shown in FIGURE 1. A spindle extension 23 is provided to serve the function of the rotating knob 20 when the end cap 21 is in place. The spindle extension 23 is removably secured in the end of spindle 13 and extends out through a hole in the top of the end cap 21.

Thus, it is seen that the hand dop assembly of this invention may be used to quickly and easily cut shapes which were heretofore very difficult even for the skilled gem cutter. The number of diiferent shapes which can be made with the hand-spin dop is limited only by the imagination. The oblong stone, practically impossible to cut accurately by hand, quickly takes shape under the imaginative hand of even the amateur lapidary.

It is also seen that the hand-spin dop assembly of the invention is also used as a companion tool for the spin dop mechanism of the copending case. Prefo rming, sanding, and polishing are more quickly and easily performed with the novel hand-spin dop.

The hand-spin dope has been especially well designed to have a sturdy and yet simple construction. Thus, it is economically manufactured and priced within the purchasing power of practically every gem enthusiast.

Although the specification describes the invention in detail it may be briefly summarized as comprising an outer body housing which may be comfortably grasped in hand, a frictionless spindle mounting carried by the outer body housing and a dop stick assembly journaled in the frictionless spindle mounting.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A hand dop assembly comprising an outer cylindrical housing of a size to be conveniently and comfortably grasped in hand, first and second ball hearing assemblies, said first bearing assembly being pressed in one end of said cylindrical housing, said second hearing assembly being pressed in the other end of said cylindrical housing, a spindle having a center -bore, said spindle be 4 ing journaled in said first and second bearing assemblies so as to be axially coextensive with the outer housing, said bearings providing frictionless spindle rotation and preventing axial spindle movement relative to said housing, portions of said spindle extending beyond the cylindrical housing at both ends, a resilient sealing ring, said sealing ring being pressed into the end of the cylindrical housing adjacent to said second bearing assembly and circumscribing the spindle to prevent the entry of foreign matter, a dop stick, said dop stick being removably secured in the center bore of said spindle.

2. A hand dop assembly comprising, an outer cylindrical housing, two bearing assemblies, said hearing assemblies being press fitted, one in each end, in the interior of said cylindrical housing, a spindle having a center bore, said spindle being journaled in said hearing assemblies for rotation, the ends of said spindle extending beyond the cylindrical housing on both ends, a sealing ring, said sealing ring being press fitted in one end of said cylindrical housing adjacent to one of said two bearing assemblies, a dop stick, said dop stick being removably secured in the center bore of the spindle at the sealing ring end of the cylindrical housing, a rotating knob, said rotating knob being removably secured to the other end of the spindle extending beyond the cylindrical housing, an end cap, said end cap being removably secured around one end of said cylindrical housing so as to cover said rotating knob, and a spindle extension, said spindle extension being removably secured in the center bore of said spindle at the end opposite said dop stick and extending out through a center hole in said end cap.

3. A gem cutters hand dop assembly comprising:

(a) a slender elongated handle, said handle sized to be grasped and facilely manipulated by the fingers of a single human hand;

(b) said handle having a bore extending longitudinally from one end;

(c) a dop stick having a gem mounting pad portion and a stem portion projecting axially from the pad portion; and,

(d) said stem portion being rotatably journaled in said handle bore with said pad portion outside said handle, said pad portion being adapted to support a gem on the side opposite said stem portion, said pad portion being disposed axially spaced from said handle and being free and clear of all dop assembly structure so that a gem secured to said pad portion may be placed against an abrasive surface whereby that a gem secured to said pad portion spins freely when placed against a moving abrasive surface.

4. A gem cutters hand dop assembly comprising;

(a) a slender elongated handle, said handle sized to be grasped and facilely manipulated by the fingers of a single human hand;

(12) said handle having a bore;

(0) a spindle rotatably journaled in said handle bore, at least one end of said spindle being accessible from outside said handle;

(d) means interposed between said handle and said spindle and preventing axial movement of said spindle relative to said handle;

(2) said spindle having a dop stick receiving opening extending longitudinally from said accessible end;

(f) a dop stick having a pad portion and a stem portion, said stern portion being disposed in said dop stick receiving opening with said pad portion outside said handle; and,

(g) means releasably locking said stemportion to said spindle.

5. A gem cutters hand dop assembly comprising:

(a) a slender elongated handle, said handle sized to be grasped and facilely manipulated by the fingers of a single human hand;

(12) said handle having a bore;

(c) a dop stick having a gem mounting pad portion and a stem portion;

(d) said stem portion being rotatably journaled in said handle bore with said pad portion outside said handle; and,

(e) a control knob connected to said stem portion and accessible from outside of said handle for rotatable manipulation of said pad portion.

6. A gem cutters hand dop assembly comprising:

(a) a slender elongated handle, said handle sized to be grasped and facilely manipulated by the fingers of a single human hand;

(11) said handle having a bore;

() a spindle rotatably journaled in said handle bore, at least one end of said spindle being accessible from outside said handle;

(:1) means interposed between said handle and said spindle and preventing axial movement of said spindle relative to said handle;

(e) said spindle having a dop stick receiving opening extending longitudinally from said accessible end; (7) a dop stick having a pad portion and a stem portion, said stem portion being disposed in said dop stick receiving opening with said pad portion disposed outside said handle;

(g) means releasably locking said stem portion to said spindle; and,

(h) a control knob operatively connected to said spindle and accessible outside said handle for rotatable manipulation of said pad portion.

7. A gem cutters hand dop assembly comprising:

(a) a handle;

(b) said handle having a bore;

(0) a spindle rotatably journaled in said handle bore, at least one end of said spindle being accessible from outside said handle;

(d) means interposed between said handle and said spindle and preventing axial movement of said spindle relative to said handle;

(e) said spindle having a dop stick receiving opening extending longitudinally from said accessible end; (1) a dop stick having a pad portion and a stem portion, said stem portion being disposed in said dop stick receiving opening with said pad portion disposed outside said handle;

(g) means releasably locking said stem portion to said spindle;

(h) a control knob operatively connected to said spindle and accessible from outside said handle for rotatable manipulation of said pad portion; and,

(i) a cap member removably secured to said handle,

said cap member covering said control knob to prevent interference with the free rotation of said control knob.

8. The combination of claim 7 wherein said handle is a slender tubular housing and said housing is sized and shaped to be comfortably grasped between the thumb and forefinger of a hand in a Writing position.

9. A gem cutters hand dop assembly comprising:

(a) an elongated slender housing having a longitudinally extending bore, said housing being sized and shaped for comfortable grasping between the thumb and forefinger of a hand in a writing position;

(b) a bearing disposed within said housing bore;

(c) gem holding means having a gem mounting head portion and a spindle portion, said spindle portion being rotatably journaled in said bearing with said head portion disposed outside of said housing and clear of all dop assembly structure so that a gem secured to said head structure may be placed against an abrasive surface; and,

(0.) said bearing permitting spindle rotation relative to said housing and preventing axial spindle movement relative to said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,520,948 Heinz Dec. 30, 1924 2,381,833 Mentzer Aug. 7, 1945 2,392,478 Holman Jan. 8, 1946 2,612,735 Lea Oct. 7, 1952 2,817,194 Leiman Dec. 24, 1957 2,977,724 Kennedy Apr. 4, 1961 3,067,551 Maginnis Dec. 11, 1962 3,071,904 Delafontaine June 8, 1963 FOREIGN PATENTS 529,298 France Sept. 6, 1921 361,662 Germany Oct. 17, 1922 541,451 Great Britain Nov. 17, 1941 

3. A GEM CUTTERS'' HAND DOP ASSEMBLY COMPRISING: (A) A SLENDER ELONGATED HANDLE, SAID HANDLE SIZED TO BE GRASPED AND FACILELY MANIPULATED BY THE FINGERS OF A SINGLE HUMAN HAND; (B) SAID HANDLE HAVING A BORE EXTENDING LONGITUDINALLY FROM ONE END; (C) A DOP STICK HAVING A GEM MOUNTING PAD PORTION AND A STEM PORTION PROJECTING AXIALLY FROM THE PAD PORTION; AND, (D) SAID STEM PORTION BEING ROTATABLY JOURNALED IN SAID HANDLE BORE WITH SAID PAD PORTION OUTSIDE SAID HANDLE, SAID PAD PORTION BEING ADAPTED TO SUPPORT A GEM ON THE SIDE OPPOSITE STEM PORTION, SAID PAD PORTION BEING DISPOSED AXIALLY SPACED FROM SAID HANDLE AND BEING FREE AND CLEAR OF ALL DOP ASSEMBLY STRUCTURE SO THAT A GEM SECURED TO SAID PAD PORTION MAY BE PLACED AGAINST AN ABRASIVE SURFACE WHEREBY THAT A GEM SECURED TO SAID PAD PORTION SPINS FREELY WHEN PLACED AGAINST A MOVING ABRASIVE SURFACE. 